This invention relates generally to conveyors and, more particularly, to extendable conveyors for loading product to, or unloading product from, a truck trailer or the like.
Retractable conveyors are permanently mounted to a warehouse dock area in the vicinity of a loading door and are incrementally extendable into the cargo area of a trailer truck. Such extendable conveyors have been provided for loading product onto the truck, in which case the conveyor may be a gravity fed roller conveyor or a driven endless belt conveyor. Such extendable conveyors have also been provided for unloading product from the trailer, in which case the conveying surface is a driven endless belt.
The prior art extendable conveyors include a base unit that is anchored to the warehouse floor and two or more extendable units which nest in the base unit when the extendable units are in a fully retracted position. The base unit typically includes horizontal support channels in order to guide the extendable units in extending and retracting movements and to bear the cantilever load of the extendable units, as well as sheet metal members in order to enclose the base unit.
Extendable conveyors in the past have utilized cable reels in order to pay out control and power electrical cables to the extendable end of the conveyor and to reel in the slack in the cables as the conveyor is retracted. Such take-up reels have been a source of equipment failure and complexity resulting from intermittent electrical connections in the commutator set.